The invention provides a timed delay circuit generating a one-shot output pulse in response to an input signal. The length of the timed delay between the input signal and the initiation of the one-shot output pulse is controlled. The timed delay until termination of the output pulse, i.e. the length or duration of the output pulse, is also controlled.
The delayed output pulse of controlled length is generated for each input signal except when a second input signal occurs before the termination of the output pulse. The delayed output pulse of controlled length is generated regardless of the duration of the input signal, even if the input signal lasts longer than the termination of the output pulse. If a second input signal occurs during the timed delay before initiation of a first output pulse or during the first output pulse itself, then a correspondent second output pulse is not generated. If the second input pulse occurs after termination of the first output pulse, then a second output pulse is generated, having a delayed initiation and controlled length.
The circuit is characterized by expanded timing range, reduced power consumption and improved adjustment resolution. Though not limited thereto, the circuit was developed for proximity switches and is particularly useful in photoelectric type proximity switches for providing a delayed output signal following a given sensed condition. The wide range together with the low power consumption makes the circuit ideal for such proximity switch application.